The coupling between intermediate metabolism and the membrane bound enzyme responsible for cation transport has been studied using 31P nuclear magnetic resonance. Our studies have localized the link to an interaction of membrane Na, K-ATPase with the membrane protein known as Band 3 and the intracellular glycolytic enzyme, glyceraldehyde 3-phosphate dehydrogenase (G3PDH). We have found that G3PDH has some of the characteristics required for it to serve as regulator of the transcellular cation transport. It has now been confirmed that Band 3 is an essential link in the transfer of conformational information from the extracellular inhibitor site of membrane Na, K-ATPase to the intracellular glycolytic enzyme complex. Studies of the interaction between the lipohilic anesthetic, halothane and red cell membrane Na, K-ATPase are also being carried out by 19F nmr. The temperature jump technique has been used to characterize the interaction of the glucose and anion transport inhibitor, phloretin, with phosphatidyl choline (PC) vesicles. It has been shown that the binding of phloretin to the PC vesicle is controlled by diffusion kinetics, whereas the debinding constant is characteristic of the vesicle-phloretin interaction. As expected, some 70% of the phloretin binding sites are on the outside of the vesicles. In connection with studies of nonelectrolyte permeation through human red cell membranes, a 13C nmr method has been developed to measure the permeability coefficient of the non-electrolyte, n-valeramide. The results obtained agree with previous values obtained by the stopped-flow method. The nmr method appears to be applicable to a variety of carbonyl containing compounds.